From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753662AbcBZMYx (ORCPT ); Fri, 26 Feb 2016 07:24:53 -0500 Received: from mail-pa0-f68.google.com ([209.85.220.68]:35008 "EHLO mail-pa0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752171AbcBZMYv (ORCPT ); Fri, 26 Feb 2016 07:24:51 -0500 Subject: Re: [PATCH v2 1/3] tracing/syscalls: Rename variable 'nr' to 'syscall_nr' To: Arnaldo Carvalho de Melo References: <1456421937-16840-1-git-send-email-treeze.taeung@gmail.com> <20160225175710.GP8720@kernel.org> <56CF4877.8000107@gmail.com> <20160225184234.GQ8720@kernel.org> Cc: Steven Rostedt , Ingo Molnar , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org, Thomas Gleixner , Lai Jiangshan From: Taeung Song Message-ID: <56D0440E.1000605@gmail.com> Date: Fri, 26 Feb 2016 21:24:46 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160225184234.GQ8720@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Arnaldo On 02/26/2016 03:42 AM, Arnaldo Carvalho de Melo wrote: > Em Fri, Feb 26, 2016 at 03:31:19AM +0900, Taeung Song escreveu: >> Hi, Arnaldo >> >> On 02/26/2016 02:57 AM, Arnaldo Carvalho de Melo wrote: >>> Em Fri, Feb 26, 2016 at 02:38:57AM +0900, Taeung Song escreveu: >>>> There is a problem about duplicated variable name i.e. >>>> # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format >>>> name: sys_enter_io_getevents >>>> ID: 739 >>>> format: >>>> field:unsigned short common_type; offset:0; size:2; signed:0; >>>> field:unsigned char common_flags; offset:2; size:1; signed:0; >>>> field:unsigned char common_preempt_count; offset:3; size:1; signed:0; >>>> field:int common_pid;offset:4;size:4;signed:1; >>>> field:int nr; offset:8; size:4; signed:1; >>>> field:aio_context_t ctx_id; offset:16; size:8; signed:0; >>>> field:long min_nr; offset:24; size:8; signed:0; >>>> field:long nr; offset:32; size:8; signed:0; >>>> field:struct io_event * events; offset:40; size:8; signed:0; >>>> field:struct timespec * timeout; offset:48; size:8; signed:0; >>>> >>>> print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: 0x%08lx, >>>> events: 0x%08lx, timeout: 0x%08lx", ((unsigned long)(REC->ctx_id)), >>>> ((unsigned long)(REC->min_nr)), ((unsigned long)(REC->nr)), >>>> ((unsigned long)(REC->events)), ((unsigned long)(REC->timeout)) >>>> >>>> As above 'int nr;' and 'long nr;' variables have >>>> duplicated name so problems are occurred in perf-script i.e. >>>> >>>> # perf record -e syscalls:* >>>> # perf script -g python >>>> # perf script -s perf-script.py >>>> File "perf-script.py", line 8694 >>>> def syscalls__sys_enter_io_getevents(event_name, context, common_cpu, >>>> SyntaxError: duplicate argument 'nr' in function definition >>>> Error running python script perf-script.py >>> >>> Please test this with 'perf trace', which this patch breaks, this patch >>> should make it understand this 3rd variation of the non common list of >>> fields in syscall tracepoints: >> >> OK, I will test it. >> But IMHO, I think the bottom change has a problem. >> Because sys_enter_io_getevent() has a argument 'long nr'. > > It doesn't matter > >> So this if statement must not have strcmp(sc->args->name, "nr") == 0. > > This is checking for the first variable, if that has that name, it > should be discarded, as in the past it wasn't there, so for the tool to > work on kernels with "nr" as the first (for the syscall number) variable > and for kernels without it, we must check and discard. > > Now we must check and discard the first "nr" (for kernels with this > meaning the syscall number) and also if it is called "syscall_nr"). > The other fields are taken as the syscall arguments, in the order that > they come, that is what what we will match with what is in the > raw_syscalls:sys_enter args array: > > [root@jouet ~]# cat > /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/format > name: sys_enter > ID: 17 > format: > field:unsigned short common_type; offset:0; size:2; signed:0; > field:unsigned char common_flags; offset:2; size:1; signed:0; > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > field:int common_pid; offset:4; size:4; signed:1; > > field:long id; offset:8; size:8; signed:1; > field:unsigned long args[6]; offset:16; size:48; signed:0; > > print fmt: "NR %ld (%lx, %lx, %lx, %lx, %lx, %lx)", REC->id, > REC->args[0], REC->args[1], REC->args[2], REC->args[3], REC->args[4], > REC->args[5] > [root@jouet ~]# > >> + if (sc->args && strcmp(sc->args->name, "syscall_nr") == 0) { >> >> I think the above instance seem better than the bottom. >> >> + if (sc->args && (strcmp(sc->args->name, "syscall_nr") || >> strcmp(sc->args->name, "nr")) == 0) { > > Right in this 'if' body we do: > > sc->args = sc->args->next; > sc->nr_args--; > > something like that. > > - Arnaldo > >> But I'll test again with perf-trace. > > Right, look at the output of 'perf trace' before and after, so that you > can check if, say, we're using that syscall_nr value as the fd for the > 'write' syscall ('fd' comes right after 'nr'/'syscall_nr'). > Sorry, I'm late. I tested perf-trace with the bottom change. (does not rename it to '__syscall_nr' on kernel) + if (sc->args && (strcmp(sc->args->name, "__syscall_nr") || strcmp(sc->args->name, "nr")) == 0) { sc->args = sc->args->next; --sc->nr_args; } But there are some problems as below. 0.322 ( 0.012 ms): a.out/27045 write(nr: 3, fd: 4196046, buf: 0x4, count: 2140 ) = 4 So, I modified the above change. (I'll send it as new patch) And then I tested again as below 0.345 ( 0.016 ms): a.out/27695 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 And I tested perf-trace with renamed '__syscall_nr' on modified kernel. Everything is ok for aught I know. 0.345 ( 0.016 ms): a.out/27695 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 I'm writing another patchset. I'll send it soon. Thanks, Taeung